Annular combustor systems

ABSTRACT

An annular combustor system is illustrated in a gas turbine engine environment. Compressor discharge air is diffused in a short length diffuser into a closely spaced plenum formed by a bluff bodied, annular array of fuel injectors and the upstream ends of liners which define, in part, an annular combustion zone. The compressor discharge air is evenly distributed in the plenum and then passes through and around the fuel injectors to break up the fuel and support its combustion in a short flame front having a uniform temperature distribution. Plenums surround the liners. Air from the diffuser pressurizes these plenums and is then metered by holes in the liners to provide cooling films on the inner surfaces thereof.

Feb. 6, 1973 United States Patent 1 Howald I ANNULAR COMBUSTOR SYSTEMS Primary ExaminerSamuel Feinberg Werner (N/Id9 Cincinnati, Ohio A!l0rney- -Derek P. Lawrence, Lee H. Sachs, Frank L.

Inventor:

Neuhauser, Oscar B. Waddell, Joseph B. Forman and James M. Kipling [73] Assignee: Angelica Corporation, St. Louis,

[57] ABSTRACT An annular combustor system is illustrated in a gas 22 Filed: Jan. 2, 1970 211 Appl.No.:353

turbine engine environment. Compressor discharge air is diffused in a short length diffuser into a closely' spaced plenum formed by a bluff bodied rannular F023 1/00 array of fuel injectors and the upstream ends of liners 60/39 74 3965 which define, in part, an annular combustion zone. The compressor discharge air is evenly distributed in [52] US. [51] Int. [58] Field of Searchmm....................

the plenum and then passes through and around the 56] References Cited fuel injectors to break up the fuel and support its com- UNITED STATES PATENTS bustion in a short flame front having a uniform temperature distribution. Plenums surround the liners. Air

2,965,303 12/1960 Jackson......i...............i... ....60/39.74

from the diffuser pressurizes these plenums and is then 2,771,744 Johnson ct al..... 3,134,229 Johnson 2,920,449

metered by holes in the liners to provide cooling films on the inner surfaces thereof.

.lohnson'et al.......................60/39.74

6 Claims, 4 Drawing Figures PATENIEUFEB 6 I975 SHEET 10F 2 INVENTOR. WE R NER E. HOWALD mummy- PATENTEUFEB 8|975 3,714,778 SHEEI 2 OF 2 INVENTOR. WERNER E. HOWALD 1 ANNULAR COMBUSTOR SYSTEMS The present invention relates to improvements in combustor systems, particularly of the type incorporated in gas turbine engines.

Gas turbine engines comprise a compressor for pressurizing an annular air stream. This pressurized air stream then supports combustion of fuel in a combustion zone to generate a high energy hot gas stream. The hot gas stream drives a turbine to power the compressor rotor and is thenconverted to a useful output, as by being discharged from a propulsion nozzle.

Combustion systems as herein contemplated include liners for defining the axial extent of the combustion zone, the means for injecting fuel into the combustion zone and the means for distributing pressurized air from the compressor and introducing it into the combustion zone. I

A common problem associated with such systems is that hot spots and/or hot streaks are created in the combustion zone which result in thermal gradients in fuser. Separation and other losses in this diffuser are minimized by a bluff body closely spaced therefrom and defining the upstream end of the combustion zone. The liners for the combustion zone extend upstream of the bluff body to form an annular plenum opening toward the diffuser discharge.

the hot gas stream discharged from the combustor v system as well as thermal gradients in the liners. The thermal gradients in the hot gas stream cause local hot spots in the turbine components to which it is discharged.

The thermal gradients in the metal parts, i.e., liners I and turbine components, limit the energy level of the .hot gas stream since temperature limitations are imposed by the hottest metal temperatures and not average metal temperatures. Also, sharp temperature gradients can induce thermal stresses which further reduce the average, safe operating temperature and the to do so has generally, in the past, increased the problems of thermal gradients.

Copending Application Ser. No. 352, filed on even date with the present application in the names of Eric S. Collinson and the present Applicant and of common assignment, discloses an effective approach to shortening a portion'of the combustor system. More specifically, that application teaches a combination of fuel injectors which reduce the length of the combustion zone and thus reduce the length and weight of the liners which define this zone.

Another object .of the invention is to reduce the length and weight of combustor systems and particularly to provide, in combination with the concepts of the above-referenced application, a combustion system of minimum length and weight wherein thermal gradients are minimized, all toward the end of enabling increases in the average temperature and energy level 'of the hot gas stream generated by the combustor system.

In its primary aspects the present invention relates to delivery of pressurized air to an annular combustion zone. Pressurized air discharged from the compressor of an'engine is diffused by a unique, short length dif- The bluff body preferably takes the form of an array of fuel injectors, each comprising a divergent cup opening into the combustion zone and a baffleplate projecting therefrom. The diffused air is evenly distributed over the upstream side of this array and flows through and around the fuel injectors to maintain a uniform,

short length flame front in the combustion zone.

Plenums also surround the liners. These plenums are pressurized by the combustor discharge and air is metered by holes in the liners to maintain a-film of cooling air along the inner'surfaces of the liners.

The above and other related objects and features of the invention will be apparent from a reading of the following description of the disclosure found in the accompanying drawings and the novelty thereof pointed out in the appended claims.

IN THE DRAWINGS;

FIG. 3 is a section taken on line IIIIII in FIG. 2; and

FIG. 4 is a section, taken on line IVIV, in FIG. 2

The'engine seen in FIG. 1 comprises a multistage, axial flow'compressor 10 which pressurizes air entering an inlet 12 at one end of a casing 14. The pressurized air is discharged from the compressor into a combustor system 16 where it supports combustion of fuel to generate a hot gas stream. Part of the energy of the hot gas stream is used to drive a turbine 18. The rotors of the turbine 18 and compressor 10 are joined by a shaft 20 to power the compressor. The remainder of the recoverable energy of the hot gas stream may be converted to a propulsive force by discharging it from a nozzle 22. Gas turbine engines take many forms and the above isintended as illustrative.

Pressurized air is discharged from the compressor 10 to an annular diffuser 26 having divergently curved, annular walls 28, 30 which are joined at their outer ends to outer and inner casings 32 and 34, respectively. The combustion zone is defined by liners 36, 38 and fuel injectors 40'at their upstream ends.

The liners 36, 38' are preferably formed in accordance with U.S. Pat. No. 3,420,058, with circumferential steps 41, through which angularly spaced holes 42 are formed generally parallel to or at an angle toward the inner surface of the liner portion downstream thereof. The holes 42 are closely spaced so mass flow of air therearound. The fuel injectors of each aligned row are formed integrally with airfoil struts 48. Fuel passageways 52 extend through the struts 48 and discharge fuel tangentially into the rear of each cup 44. The fuel is broken up by a vortical flow of air through the tangential slots 50 formed in each cup 44 and then further broken up by the vortical flow of air around the peripheries of the baffle plates 46. The air vortices and the multiple injector form a very short and stable flame front in the combustion zone, as is more fully described in the referenced, copending application.

Reverting to the diffuser 26, it will be noted that its divergently curved walls 30, 28 have an extreme curvature and that, for its axiallength, the diffuserhas an area ratio area out/area in) much greater than conventional diffusers of the wall-attachment type. The diffuser is more particularly characterized ashaving an inlet height, h, to axial length, 1, ratio (h/l) of 4/1 or less and an area ratio of 2.5/1 or greater. The described difthe discharge height of the diffuser and lying in a plane generally normal to the direction of air flow from the diffuser. Further, the liners 36, 38 project upstream of the bluff body formed by the baffle plates 46 providing an annular plenum having its center of'area aligned with the center of area of the annular diffuser 26. This arrangement most efficiently turns the compressor discharge air around the curved diffuser walls 30, 28 with little or no separation.

As the compressor discharge air is thus diffused, its velocity is proportionately reduced and then further reduced as it flows into the annular plenum. Such a significant reduction in air velocity provides an equal pressure distribution over the upstream sides of the fuel injectors with a minimum of losses.

The equal pressure distribution within the annular plenum enables the fuel injectors 40 of each circumferential row to be manufactured with identical configurations providing equal mass flow rates of air to each injector. With equal fuel flow rates to the injectors, the rate of combustion at each injector is accurately and evenly controlled within a localized area of the relatively short flame front immediately downstream of the fuel injector array.

In this latter connection, it will be noted that essentially all of the air for the combustion process to be carried out, in the combustion zone of the combustor, is introduced through and around the fuel injectors 40. With the described equalized distribution of air flow the combustion process is highly uniform in a circumferential sense to minimize thermal gradients. The

minimal thermal gradients further minimize the axial purpose of diluting any hot streaks in the combustion stream as is common in conventional combustors. The

cooling air is metered by the holes 42 to provide an essentially uniform insulating film on the inner surfaces of the liners which is replenishedby each succeeding, circumferential row of closely spaced holes.

In this connection it will be noted that the annular spaces between the liner 36 and outer casing 32 and between the liner 38 and the inner casing 34, respectively form plenums having essentially uniform pressure and flow velocity therein. Compressor discharge air flows freely from the diffuser 26 through annular openings, defined by the upstream edges of the liners 36, 38, into these plenums. The upstream edges of the liners 36, 38 are in the form of thickened lips 60 to accelerate the air and minimize turning losses as it enters the cooling air plenums. While there-may be other components supplied with cooling air (or compressor discharge air) from these plenums, the entrances thereto are sufficient to maintain the aforereferenced equal, or controlled, pressure distributions. This rela- Ltionship is significant in maintaining a predetermined,

uniform distribution of cooling air along the inner surfaces of the liners 36, 38.

Variations in the preferred embodiment, disclosed herein, will occur to those skilled in the art within the spirit and scope of the present inventive concepts as defined by the following claims. I

Having thus described the invention, what is claimed as novel and desired to be secured by Letters Patent of the United States is:

1. A combustor system for generating a hot gas stream by the combustion of fuel in a pressurized air stream discharged from a compressor, said system comprising,

a pair of liners respectively defining the inner and outer bounds of an annular combustion zone, an annular bluff body at the upstream ends of said liners, means for injecting fuel'into said combustion zone adjacent said bluff body, said bluff body having a plurality of evenly distributed openings thereto for the introduction of pressurized air into said combustion zone, an annular diffuser connected at its upstream end to the compressor discharge and diverge'ntly curved to provide high pressure, low velocity air evenly distributed over the-upstream side of said bluff body for introduction into said combustion zone, wherein an annular plenum is formed upstream of said bluff body and opening toward said diffuser discharge, and wherein the annular diffuser has a ratio of its inlet'height to its axial length of no greater than approximately 4:1 or less and an area ratio of at least approximately 2.511. 2. A combustor system for generating a hot gas stream by the combustion of fuel in a pressurized air stream discharged from a compressor, said system comprising,

a pair of liners respectively defining the inner and outer bounds of an annular combustion zone, an annular bluff body at the upstream end of said liners, means for injecting fuel into said combustion zone adjacent said bluff body, said bluff body having a plurality of evenly distributed openings therethrough for the introduction of pressurized air into said combustion zone,

an annular diffuser connected at its upstream end to the compressor discharge and divergently curved to provide high pressure, low velocity air equally distributed over the upstream side of said bluff body for introduction into said combustion zone, wherein an annular plenum is formed upstream of said bluff body and opening toward said diffuser discharge, and wherein the bluff body is in the form of a plurality of angularly and radially spaced fuel injectors, each fuel injector comprising a cup opening toward said combustion zone and having a plate projecting outwardly from said cup, the plates of said fuel injectors being spaced apart from each other and spaced from adjacent liners to provide openings for the introduction of pressurized air into said combustion zone, each fuel injector further comprising a passageway for the introduction of fuel into said cup and tangential slots in said cup for introduction of further pressurized air into said combustion zone.

3. A combustion system as in claim 2 wherein, the diffuser has a ratio of its inlet height to its axial length of no greater than approximately 4/1 and an area ratio of at least approximately 2.5/1.

4. A combustion system as in claim 3 wherein,

casings are respectively spaced from the outer surfaces of said liners to form liner plenums,

said liners extend upstream of the plates of said fuel injectors to form the annular plenum opening towards said diffuser discharge, the upstream edges of said liners being spaced from said diffuser to define entrances to the liner plenums and the liners have openings therethrough for the introduction of cooling air along their inner surfaces.

5. A combustion system as in claim 4 wherein, the entrances to said liner plenums are in the 'form of nozzles to accelerate the air entering the plenum and thus minimize entrance losses.

6. A combustion system as in claim 5 wherein, the liners have circumferential steps along their lengths and the openings in the liners are in the form of holes through said steps, directing cooling air along the interior surfaces of the liner immediately downstream of the respective steps. 

1. A combustor system for generating a hot gas stream by the combustion of fuel in a pressurized air stream discharged from a compressor, said system comprising, a pair of liners respectively defining the inner and outer bounds of an annular combustion zone, an annular bluff body at the upstream ends of said liners, means for injecting fuel into said combustion zone adjacent said bluff body, said bluff body having a plurality of evenly distributed openings thereto for the introduction of pressurized air into said combustion zone, an annular diffuser connected at its upstream end to the compressor discharge and divergently curved to provide high pressure, low velocity air evenly distributed over the upstream side of said bluff body for introduction into said combustion zone, wherein an annular plenum is formed upstream of said bluff body and opening toward said diffuser discharge, and wherein the annular diffuser has a ratio of its inlet height to its axial length of no greater than approximately 4:1 or less and an area ratio of at least approximately 2.5:1.
 1. A combustor system for generating a hot gas stream by the combustion of fuel in a pressurized air stream discharged from a compressor, said system comprising, a pair of liners respectively defining the inner and outer bounds of an annular combustion zone, an annular bluff body at the upstream ends of said liners, means for injecting fuel into said combustion zone adjacent said bluff body, said bluff body having a plurality of evenly distributed openings thereto for the introduction of pressurized air into said combustion zone, an annular diffuser connected at its upstream end to the compressor discharge and divergently curved to provide high pressure, low velocity air evenly distributed over the upstream side of said bluff body for introduction into said combustion zone, wherein an annular plenum is formed upstream of said bluff body and opening toward said diffuser discharge, and wherein the annular diffuser has a ratio of its inlet height to its axial length of no greater than approximately 4:1 or less and an area ratio of at least approximately 2.5:1.
 2. A combustor system for generating a hot gas stream by the combustion of fuel in a pressurized air stream discharged from a compressor, said system comprising, a pair of liners respectively defining the inner and outer bounds of an annular combustion zone, an annular bluff body at the upstream end of said liners, means for injecting fuel into said combustion zone adjacent said bluff body, said bluff body having a plurality of evenly distributed openings therethrough for the introduction of pressurized air into said combustion zone, an annular diffuser connected at its upstream end to the compressor discharge and divergently curved to provide high pressure, low velocity air equally distributed over the upstream side of said bluff body for introduction into said combustion zone, wherein an annular plenum is formed upstream of said bluff body and opening toward said diffuser discharge, and wherein the bluff body is in the form of a plurality of angularly and radially spaced fuel injectors, each fuel injector comprising a cup opening toward said combustion zone and having a plate projecting outwardly from said cup, the plates of said fuel injectors being spaced apart from each other and spaced from adjacent liners to provide openings for the introduction of pressurized air into said combustion zone, each fuel injector further comprising a passageway for the introduction of fuel into said cup and tangential slots in said cup for introduction of further pressurized air into said combustion zone.
 3. A combustion system as in claim 2 wherein, the diffuser has a ratio of its inlet height to its axial length of no greater than approximately 4/1 and an area ratio of at least approximately 2.5/1.
 4. A combustion system as in claim 3 wherein, casings are respectively spaced from the outer surfaces of said liners to form liner plenums, said liners extend upstream of the plates of said fuel injectors to form the annular plenum opening towards said diffuser discharge, the upstream edges of said liners being spaced from said diffuser to define entrances to the liner plenums and the liners have openings therethrough for the introduction of cooling air along their inner surfaces.
 5. A combustion system as in claim 4 wherein, the entrances to said liner plenums are in the form of nozzles to accelerate the air entering the plenum and thus minimize entrance losses. 